Search Publications
The Density and Masses of Obscured Black Holes
Comastri, Andrea; Fiore, Fabrizio
Recent Chandra and XMM-Newton surveys have uncovered a large fraction of the obscured AGN responsible of the hard X-ray background. One of the most intriguing results of extensive programs of follow-up observations concerns the optical and near-infrared properties of the hard X-ray sources counterparts. More specifically, for a significant fractio…
HST/STIS observations of sdBV stars: testing diffusion and pulsation theory
Heber, U.; Chayer, P.; Fontaine, G. +3 more
We present the initial results of an abundance analysis of echelle UV spectra of five hot subdwarf B (sdB) stars. These stars have been identified as core helium burning objects on the extreme Horizontal Branch. Around 5% of sdBs show short-period acoustic-mode oscillations. Models predict that these oscillations are due to an opacity bump caused …
A new mechanism for the crab fingers
Carlqvist, P.
Images of the outer filamentary parts of the Crab Nebula, earlier obtained with the Hubble Space Telescope WFPC2, are reconsidered. On inspection of the images it is found that most of the mainly radially oriented fingers possess an internal structure, usually in the form of two or more filaments. For some of the fingers there are clear signs that…
Photometric analysis of EL Aqr
Wadhwa, Surjit S.; Zealey, William J.
We present an analysis of the Hipparcos and ASAS photometry of the W UMa star EL Aqr. The Wilson-Devinney code is employed in conjunction with recent spectroscopic mass ratio of 0.203 to model the V band light curve. We confirm that the system is an A type contact binary however our analysis suggests that it is over massive for its spectral class …
Evidence for an Ionized Rotating Structure Around RW Aur
Gómez de Castro, Ana I.; Verdugo, Eva
Profiles of the UV semiforbidden lines of C III and Si III of RW Aur have been obtained with the HST/STIS. The C III profile shows two high velocity components at v = +/- 170 km s-1 and a central one. The Si III profile is very broad (FWHM = 293 km s-1) and the high velocity components are unresolved. It is shown that the hig…
X-rays from the Local Bubble
Freyberg, Michael J.
Thermal plasma emission in the soft X-ray band (0.1–2.0 keV)is believed to be responsible for the bulk of the X-ray intensityseen from the Local Bubble, a low-density cavity extending over∼ 70–200 pc around the Sun. The state of the hot plasmais still a matter of discussion as previous instrumentation like aboardROSAT was not able to unambiguously…
Diffuse Baryons in Cosmic Structures
Cavaliere, Alfonso
I review the processes that govern the amount and the thermal state of the hot plasma pervading clusters and groups of galaxies: the gravitational heating driven by the DM merging histories, the radiative cooling of baryons, and the energy fed back by SNe and by AGNs or quasars. I argue that the X-ray emissions and the entropy levels now observed …
The XMM-Newton Bright Serendipitous Survey: First Extragalactic Results
Wolter, Anna; Maccacaro, Tommaso; Braito, Valentina +3 more
We present here some initial results from the ongoing XMM-Newton bright serendipitous survey. The survey is aimed at selecting and spectroscopically identifying a large and statistically representative sample of bright (fx ≳ 7× 10‑14 c.g.s) serendipitous X-ray sources in the 0.5–4.5 keV energy band (BSS) and a complementary (…
Mid-Infrared properties of Early-type galaxies
Madden, S. C.; Vigroux, L.; Xilouris, E. M.
We have conducted a survey of early-type galaxies using the ISOCAMinstrument on board the Infrared Space Observatory (ISO)in order to probe their dustcontent. We present Mid-Infrared photometric properties for a sampleof 20 galaxies observed at 4.5, 7 and 15 µ$m. Using diagnosticcolor-color diagrams, we can delineate the different Mid-Infrar…